Resizing an image on your Mac is simple with Preview, a free image utility that comes pre-installed on OS X. Preview helps you crop images easily and adjust their dimensions without having to install additional software. Learn how to gain control over the size of your photos, remove unwanted areas, and adjust the resolution for various uses with Preview.

Steps

Method1

Resizing an Image in Preview

1

Navigate to the image you wish to resize. This method will help you change the size of the entire image. If you want to crop out a part of the image to resize, see Cropping an Image in Preview.

To search for an image name or tag, open Finder, then click the magnifying glass icon in the menu bar. Type in your search criteria and press ⏎ Return to show your results.

2

Drag the image to the Preview icon in the Dock or Finder.[1] This will open the image in Preview.

You can also right-click the image and select “Open With” and then “Preview.”

3

Click the edit button (a square with a pencil) to switch to Edit Mode. This will launch a new toolbar at the top of the Preview window.

4

Click the “Tools” menu and select “Adjust Size”.

5

Change the resolution.[2] Resolution is measured in pixels per inch (also called “dots per inch” or “dpi”). If you plan to print your image or simply want it to retain as much of its quality as possible, consider raising the resolution.

If your image is for the web or for use in an app like Facebook, the default (72) is fine. If you start with a higher resolution, reducing it will give you a smaller file size.

If you plan to print your image in a high-quality format, such as for advertisements or other forms of business communications, set it to at least 600. Note: this will raise the size of the file significantly.

To print glossy photos, 300 will suffice. The file size will be much larger than that of a default 72 dpi image, but the final quality will be worth it.

6

Type your desired width and height in the designated boxes. The larger the width and height, the larger the file size.

It may be helpful to change the unit of measurement to best visualize your image. For example, you can change it to “cm” if you want to specify the width in centimeters. Click the drop-down right next to both Width and Height to make your selection.

If you would prefer, you can choose the size by selecting a percentage of the current size. Select “Scale,” then choose a percentage from the drop-down.

7

Place a check next to “Scale proportionally” to avoid warping the image.[3] This is optional, but you can use this option to make sure that setting the width also modifies the height. This ensures that the image retains its original proportions.

8

Click OK to view the image at its new size. If you are dissatisfied with the changes, press ⌘ Cmd+Z to undo them.

Community Q&A

When I make changes to the image, it does not appear to keep the changes. The image is still at the wrong dpi as well.

wikiHow Contributor

You can try to export the image to different file formats by going to the menu bar and click on "File>Export." This will create a new file in the type you specified with the resized settings. Be sure you are opening the file you duplicated rather than the original file if they are placed in different locations.

About this wikiHow

"This was so helpful! I had been trying for hours to set up my email signature through Mail on my Mac, which includes some graphics. No matter what, I did I could not get the size correct - it was always huge. I finally was able to use preview to resize and get what I needed."..." more

Rated this article:

HS

Harinder Sethi

Nov 30, 2016

"Reducing was required for Indian OCI forms from higher KB size photo to lower size, within certain pixel size. This article was helpful in doing that."..." more

BD

B. D.

Jul 14

"Great tutorial. Helped me to learn how much Macs have built in that I just need to learn how to use."

A

Anonymous

Jan 6

"Learning how to open the markup button and the edit mode was helpful. "